Method of repairing thread rolling dies



Sept.-6, 1960 s. B. KATz ETAL METHOD OF REPAIRING THREAD ROLL ING DIES Filed March a, 1957 2 Sheets-Sheet 1 ,/5 L IT:I\A k5 FIE a INVQENTORJ J15. hA-rz BY CHEEHE Sept. 6, 1960 s. s. KATZ ETAL 2,951,283

METHOD OF REPAIRING THREAD ROLLING DIES Filed March 8, 1957 2 Sheets-Sheet 2 ?0 i N Fig 7 INVENTORJ 9 r F U 7 o 51m 71 BY F6 -J. CHEF-Ha fii QW United States Patent Ofiicc 2,951,23 Patented Sept. 6, 1960 This invention relates to the art of thread rolling and particularly to improvements in the method of repairing dies used in conjunction therewith.

Specifically the invention involves the method of repairing flat rolling dies and means to improve not only the threads produced thereby, but also to increase the length of life of the same as well as the uniformity of threads rolled thereby during such life.

The fact that the invention is adapted to be used for salvaging dies which have been damaged is a further indication of the advance in the art accomplished hereby.

Generally speaking, a number of problems arise in connection with flat die thread rolling, among them being the fact that the blanks to be threaded, lack uniformity or are formed with shoulders or other imperfections that affect the final thread.

In addition to the foregoing, damage to the dies them starting end of a die face, so as to enable satisfactory threading of blanks which would otherwise be rejected, because of some defect therein, which defect may be compensated for hereby.

A further object hereof is to modify the form of thread forming elements of a die face in such a manner as to enable the rolling of threads on somewhat harder material than that heretofore used, under certain circumstances and for a particular type of blank or type of material from which the blank is itself made.

Yet another object of the invention is to provide a thread face formation on flat rolling dies, which in effect preliminarily conditions the blank during initial movement, whereby continued further manipulation of the blank will be effected to produce uniform threads thereon, irrespective of initial minor defects in the blanks to be threaded.

Another object of the invention is to provide thread rolling die members which will minimize, if not completely eliminate, distortion of the thread profile owing to compression, bending, chipping or crumbling among others, of the thread forming elements of the said die members.

A further important object is to provide a method of salvaging dies of the class herein described, whereby the same may again be used for thread rolling purposes.

Yet another object hereof is to provide threading dies in which the thread forming elements are substantially modified in certain aspects, yet the rolling operation prodies.

Other and further objects and advantages of the invention will be understood from a consideration of the specification and claims herein, and shown in the drawings, wherein:

Figure 1 is a somewhat diagrammatic disclosure of a flat die rolling arrangement, showing certain of the known features thereof and the relationship of the improvement provided by this invention to such dies.

Figure 2 is a fragmentary view in perspective taken from one end showing usual die members and indicating the modification thereof.

Figure 3 is a greatly enlarged, fragmentary section of the end, of a flat die member, showing the usual thread elements prior to changes in accordance with the invention and indicating the location of the changes in certain aspects.

Figure 4 is a view like Figure 3 with the elements modified in accordance with the teachings of this invention.

Figure 5 is a greatly enlarged fragmentary view taken looking down on the upper surface of a die member modified in accordance with this invention.

Figure 6 is a view taken from the side of Figure 5, likewise being greatly enlarged and indicating the manner of modification hereof.

Figure 7 is a somewhat enlarged view showing a typical blank to be rolled by the dies modified in accordance with this invention and indicating imperfection therein.

Referring now to Figure 1 in order to relate the improvements of this invention to the usual practice in thread rolling, it will be understood that in accordance with the conventional practice a moving die body 1 is provided, the die body being generally rectilinear in formation and including ends 2 and 3 arranged at the usual-angle for holding the die in position in the machine, the machine itself being obviously omitted as it is well known in the art.

The usual stationary die 4 is likewise provided having the ends 5 and 6 incorporating the holding angle therein.

As is also clearly and well known, the die bodies 1 and 4 may be arranged so as to move with respect to one another in the usual manner as the moving die is the moving member, and in so doing since the face of each, is equipped with thread forming elements will form threads upon a blank such as 7 shown in position between the respective members 1 and 4 as being located by the starting finger 8.

In this instance and for the sake of the explanation appended hereto, reference will be made to the blank 7 as comprising a pipe plug blank as shown in enlarged detail in Figure 7, including a body. portion 9 and a square section 10 by which the plug is positioned when used as will be readily understood.

The stationary die 4 of Figure 1 is equipped with the usual starting relief configuration as shown in that View indicated at 11 and similarly the relief at 12 at the other end of the stationary die body 4. Other details of the arrangement of Figure 1 will be referred to after the detailed description of the modification hereof is set forth, reference being particularly had to the dotted line indication at 13 in the moving die body 1 and at 14 in the stationary die 4. The purpose of these dotted lines 13 and 14 is to indicate the modification of the thread faces which is explained more in detail in reference to Figures 3 to 6 inclusive.

Referring now to the said Figures 3 to 6 inclusive and the die body of Figure 2 for the purposes hereof being the stationary die body 4, including the face 6 thereof, it will be seen that the enlarged fragmentary views of Figures 3 and 4 illustrate on the one hand that in Figure 3 the thread forming elements such as indicated at 15 are of the usual triangular form having crests at 16 and roots at 17. As has been indicated heretofore the die bodies 1 and 4 are in this case provided with the thread forming elements 15 to roll threads on pipe plugs such as 7 and the crests 16 and roots 17 are thus sharp to form the threads properly on the blanks.

The invention hereof is related to modification of the thread forming elements 15 as by truncating the same at the starting end of each of the die bodies 1 and 4 for example, substantially as indicated in Figures 3 and 4, by grinding to cause the truncation of the apices or crests of the thread forming elements 15 to about /3 the original height thereof. This is accomplished after the manner indicated in Figure 5 and likewise in Figure 6 by positioning the end 6 for example of the die body 4 on the surface plate of a grinder, raising the same sufirciently to reduce the height of the thread from root to crest by the 6 amount indicated as the truncation is effected, the longitudinal extent of such truncation being about equal to twice the circumference of the blank upon which the thread is to be rolled.

Explaining the foregoing more in detail and referring to Figures 5 and 6, it will be seen that at the left hand end of Figure 6, the portion of the thread indicated by the cross shading is ground down for about the amount indicated at D and the lengthwise extent of such grinding operation extends from the end A of the elements to the point indicated at B where the actual amount of removal of the material or truncation is reduced to zero. As indicated the overall length of this truncation is no less than a distance equal to the circumference of the blank to be threaded and preferably equal to or slightly in excess of twice the circumference of such blank.

As viewed in Figure 5 the crests of the threads will therefore appear somewhat as indicated by the cross shading and it will be noted that the roots of the thread forming members are not disturbed or otherwise affected.

In changing the initial thread rolling portions of the die bodies 1 and 4 as above indicated, by grinding the same to truncate the threads along the lines described, it has been found that even though the blanks such as shown in Figure 7 denoted 7 are not entirely accurately formed,.

they may be threaded and not necessarily damage the thread forming elements. The blanks may actually have at the upper extremity of the portion to be threaded as at 20, an imperfection such as a bulge or other slight out of round condition, and yet the truncation of the threads at the initial portions of the thread rolling sections of the die bodies as described, in effect compels the blank to undergo what might be described as a blanking operation resulting in preliminarily conditioning the blank so as to zubsequently have imparted thereto the proper thread orm.

It should be pointed out in connection with the foregoing that the portion of the thread forming elements 4 for example extending from point B, reference being had here to the Figure 1 disclosure, to the ends C therein, is such that the elements are of the usual sharp crested type and of sutficient extent to equal in length at least, the circumference of the blank being threaded and preferably twice that circumference in order to positively provide satisfactory threads upon the surface of the blank.

It will of course be understood that the thread forming elements of the moving die body 1 are similarly ground and to the equivalent extent of the section AB of the die body 4.

Referring momentarily to the Figure 2 disclosure, it will be seen that the thread forming elements of the thread rolling face, are arranged so as to form taper threads on a pipe plug blank such as 7, the elements being,

formed on the face of the die body 4 to provide for a pair of thread rolling surfaces as indicated at 25 and 26 in accordance with conventional practice generally.

It is also pointed out that if a die of the usual formation is provided and owing to imperfections in the blanks, crumbling or other distortion or destruction of the crests of the threadrolling elements takes place, the die body.

rolling blanks eitheroversized or of inconsistent size, the

same may in many cases be treated according to the invention herein and. thus, be usable for the production of threads on large numbers of the parts or blanks subsequently. The actual truncating operation or grinding as the case may be, often times removes entirely the damaged portions of the threadforming elements and where such removal is not entirely completed nevertheless enables the die bodies to be used to roll satisfactory threads on many thousands of pieces thereafter. The foregoing is particularly likely to be true because damage to the thread forming elements of conventional die bodies usually occurs in the portions thereof which first contact the blank and along which the thread form begins to be imparted thereto, since the most radical change in the blank occurs during movement along those portions.

We claim:

1. The method of salvaging a flat thread rolling die in which the thread forming elements of the flat die face have been damaged, which comprises causing the apices of such elements to be truncated for approximately one-third of their length beginning at the starting end thereof, said truncation being initially substantial at said starting end of the Hat die and diminishing uniformly over a distance equivalent to at least the circumference of the blank on which the die is designed to form the threads.

2. The method of salvaging a flat thread rolling die in which the thread forming elements of the flat die face have been damaged, which comprises causing the apices of such elements to be truncated for approximately onethird of their length beginning at the starting end thereof, said truncation being initially substantial at said starting end of the flat die and diminishing uniformly over a distance equivalent to at least the circumference of the blank on which the die is designed to form the' threads, said thread forming elements thereafter being of uniform section for a distance equivalent to at least the circumference of such blank aforesaid.

3. The method of salvaging a flat thread rolling die in which the thread forming elements of the flat die face have been damaged, which comprises causing the apices of such elements to be truncated for approximately one-third of their length beginning at the starting end thereof, said truncation being initially substantial at said starting end of the flat die and diminishing uniformly over a distance equivalent to approximately twice the circumference of the blank on which the die is designed to form the threads.

4. The method of salvaging a flat thread rolling die in which the thread forming elements of the flat die face have been damaged, which comprises causing the apices of such elements to be truncated for approximately onethird of their length beginning at the starting end thereof, said truncation being initially substantial at said starting end of the flat die and diminishing uniformly 5 over a distance equivalent to approximately twice the circumference of the blank on which the die is designed to form the threads, the thread forming elements being thereafter of uniform section for a distance equal to at least the circumference of the blank aforesaid.

References Cited in the file of this patent UNITED STATES PATENTS 368,688 Rogers Aug. 23, 1887 6 Simonds Feb. 24, 1891 Wilcox July 10, 1917 Frayer Apr. 26, 1932 Lammond Oct. 4, 1932 Stimson May 28, 1940 Erdman May 19, 1942 

